(cyclopentadienyl) Zirconium Complex Catalyst For Ethylene And Propylene Oligomerization - Cyclization Reaction

The one-pot oligomerization-cyclization of ethylene or propylene catalyzed by Cp2ZrC12 with EAO (ethylaluminoxane) or Et3AI as cocatalyst is a newly founded interesting reaction. We have investigated the effect of reaction conditions, such as solvents, aging temperature, reaction temperature, reaction time, reaction pressure,the concentration of pro-catalyst, the ratio of Al/Zr, the hydrolysis extent of Et3AI and the addition of third- component, on the catalytic activity and selectivity to low carbon olefins, especially to five-membered carbocyclic compounds. The cyclization mechanism of ethylene and propylene is discussed. We found that in addition to common oligomers, the oligomerization of ethylene catalyzed by Cp2ZrCI2 with EAO or Et3A1 as cocatalyst also afforded an unexpected cyclic product, methylenecyclopentane(MCP).With different solvents, under the same conditions the order of activities for the oligomerization of ethylene is as follows: chlorobenzene>toluene>cyclohexane. The use of toluene or cyclohexane as solvent comparatively favored the formation of monocyclic product. Both aging and reaction of temperature proved to be important factors in optimizing the selectivity for cyclic product. With comprehensive consideration of activity and selectivity, The proper aging temperature is under 100 0C and the favorable temperature for cyclization of ethylene and propylene is in the range of I 50梚 70 0C . The concentration of Cp2ZrCI2 has a great influence on the activity. When the concentration of Cp2ZrC12 was decreased from I.67X iO~ to 8.33 X lO4mmol/ml, the activity grew from 416 to 731g(oliomers) /g(Zr)h. In the meantime the selectivity of methylene cyclopentane and low carbon olefins did not present an obvious change. The selectivity of five membered carbocyclic compounds depends apparently on the ratio of Al/Zr. Under the same conditions, as the increase of the ratio of Al/Zr from 25 to 100, the selectivity of cyclic product increased apparently, but with higher Al/Zr ratio, the selectivity to MCP decreased slightly. The decrease of hydrolysis extent of Et3A1 resulted in an upgrading tendency towards the selectivity to MCP for the oligomerization of ethylene. When unhydrolyzed Et3A1 (A1IZrIOO) was used in place of EAO as cocatalyst, the selectivity of MCP increased from 28% to 39%, and the activity was 559g(oligomers)/g(Zr)h. The addition of basic third-component, such as C5H5N and Et3N to the Cp2ZrCI2/EAO system, is capable of improving the selectivity to MCP, e.g. when the oligomerization of ethylene catalyzed by the tn-component catalytic system Al/Zr/C5H5N, the selectivity of MCP rose to 37%, and the activity was 461g(oligomers)g(Zr)h. The addition of Ph3P did not show an evident influence on the selectivity to MCP. The oligomerization of propylene catalyzed by Cp2ZrC12 with EAO as cocatalyst gave two substituted cyclopentanes (1,1,3- tnimethycyclopentane and 1,1,3 ,4-tetramethycyclopentane) along with C6 and C7 chain oligom鑢s. We have investigated the effect of reaction temperature, reaction time, the ratio of Al/Zr and the reaction pressure on the catalytic activity and selectivity to five- memebered carbocyclic compounds. The effect of reaction temperature, reaction time, the ratio of Al/Zr on the oligomerization-cyclization of propylene followed the similar regularity as those for ethylene reaction, The favorable reaction...